Ordinary roads and railroads smooth our passage over the surface of the earth, but bridges and tunnels create a path where none existed before, either spanning free space or burrowing through the solid earth.

Bridges make connections; they bring people together—a role that has made them a traditional emblem of friendship. Consider the town of Mostar in Bosnia-Herzegovina. When fighting between ethnic factions broke out there in the 1990s, nothing symbolized the social disintegration more clearly than the destruction of a sixteenth-century stone-arch bridge that had linked the two parts of the town on opposite banks of the Neretva River. And the emblem of efforts to heal the divisions is a rebuilt bridge, opened with fireworks and fanfare in July of 2004.

Bridges themselves, in many cases, are looked upon with affection. Whereas many other large engineered structures—refineries, power plants, highways, airports—tend to be seen as a blot on the landscape, bridges are granted an exemption. San Franciscans don’t complain that the Golden Gate Bridge is a desecration of the Bay. And Sydney, Australia, considers its Harbour Bridge one of the city’s main tourist attractions. Even some tunnels have a bit of romance attached to them, although it tends to focus more on the perilous process of digging the passage rather than on the finished artifact.

Bridges

There are 589,685 highway bridges in the United States. I haven’t counted them, but the statisticians at the Federal Highway Administration have. They have counted, measured, rated, classified, and tabulated, and 589,685 was the total they came up with in the most recent census, at the end of 2001. Across town at the Federal Railroad Administration no one claims to have an exact count—is it a less obsessive bureaucracy, or just less well funded?—but in 1993 they estimated there were about 100,000 bridges carrying railroad tracks.

When we think of bridges, it is the dramatic and monumental long spans that come to mind first, especially the graceful suspension bridges such as the Golden Gate and the Brooklyn Bridge. But the great majority of those hundreds of thousands of bridges in the United States are not such spectacular structures. They are ordinary overpasses, with spans of 30 or 40 feet, carrying roadways or rails across other thoroughfares or over small streams. You see such bridges by the dozen on any drive down the Interstate. They may be lacking in glamour, but they are most representative of the bridge builder’s art.